The companion paper FBT01A identifies the three-κ system (κ0, κ1, κ2) as the complete scalar geometric readout of the six-dimensional symplectic carrier (B6,Ω) in the Fracture–Berry–Tension (FBT) framework. The present paper proposes a restricted physical reading of that system, focused only on effective gravitational coupling. The central claim is conjectural rather than derived. Among the three scalar quantities, the reduced dual-phase area κ1 is argued to be the most natural candidate for controlling an effective four-dimensional gravitational coupling. The argument is structural: κ0 measures the total Liouville capacity of the full carrier and is therefore too coarse to isolate the internal contribution, whereas κ2 is a local mixed-channel density and is therefore better interpreted as a scale-dependent modulation. By contrast, κ1 is global on the internal dualphase sector and thus is the most plausible bridge between internal geometry and an effectivefour-dimensional coupling. On this basis, we formulate a gravitational closure conjecture of the schematic form Geff κ1 = F(κ0), which reduces to a constant-product relation once a normalization convention for the total Liouville volume is fixed. The paper makes no claim to derive Newton’s constant numerically and deliberately avoids stronger assertions concerning Planck’s constant, mass formulae, or phenomenology. Its aim is narrower: to isolate the gravitationally most natural role of κ1 within the three-κ system and to state the resulting conjecture in the cleanest possible form.